1. Field of the Invention
This invention relates generally to spherical i.e. ball an socket, bearings and more particularly to bearing configurations which provide desired electrical conductivity characteristics between a bearing body and a bearing housing.
2. Background History
Ball and socket bearings have been employed in conjunction with drive systems wherein shafts were not in alignment. Such bearings included a bearing body having a ball, spherical, or a spherical sector shaped surface, that is, a convex surface defined by a sphere cut along two parallel planes equidistantly spaced from its geometric center. The bearing bodies included either a single or a plurality of sector shaped surfaces.
The bearing body was seated in a two part housing having mating concave socket surfaces The housing parts were separated along a plane passing through the geometric center of the socket as well as the bearing body.
To assemble the bearing with a shaft in a drive system, the housing parts were not tightly connected until the shaft and housing were positioned in the system. The body and shaft self aligned relative to the housing during positioning
After positioning, the housing parts were tightened together and the bearing body was prevented from further movement relative to the housing. During normal operation the bearing body did not move relative to the housing in order to preclude wear on both the convex bearing body surfaces and the concave socket surfaces.
In order to prevent unlimited random movement of the bearing body relative to the housing during assembly, a motion limiting pin projected radially from the body. The pin was received in an oversized recess in the concave socket surface. The body remained capable of movement relative to the housing for adjustment of the shaft and body. Movement was limited by contact between the positioning pin and a wall of the recess.
In some drive system applications, the bearing body and shaft were required to be electrically connected with the housing, e.g. to divert electrical currents or charges. In other applications, however, it was desired to electrically isolate the bearing body from the housing, e.g. to preclude electrical creep currents which could result in electrolytic action at mating surfaces.
When electrical isolation was not required, the convex spherical surface of the body was in direct contact with the concave socket surfaces of the housing and a metal positioning pin was utilized. If electrical isolation was required, it was necessary to electrically insulate the positioning pin from the housing and, in addition, a layer of electrically insulating material was required to be placed between the bearing body and the convex socket surfaces of the housing.
As a result, for drive systems having the same working load and drive system dimensional requirements different housings and/or bearing bodies were required, depending upon the electrical conductivity characteristics specified. In order to accommodate the thickness of the insulating layer positioned between the bearing body and the housing in electrically isolated applications, one was required to employ either two different sizes of bodies or housings, one for the assembly of an electrically isolated bearings and one for the assembly of electrically conductive bearings.
Additionally, bearing bodies and housings were required to be manufactured within strict dimensional tolerances because of the fit required between the mating convex and concave surfaces of the body and the housing as well as to assure that the housing parts were joined and sealed oil tight.